Interspecies assessment factors and skin sensitization risk assessment

For many endpoints in toxicology, an interspecies safety factor remains a standard requirement. However, for skin sensitization, the hazard and potency predictions, notably from the local lymph node assay (LLNA) have been shown to correlate well with human data. Despite this, there are always exceptions, both over and under predictions. For this reason it has been suggested that an interspecies factor of 15 would accommodate potential "errors". An alternative approach is suggested in which an evidence-based strategy is taken: the large majority of the information indicates a human:LLNA ratio of 1, therefore a corrective factor would best be applied where our knowledge of the underlying chemistry of sensitization indicates that it is necessary.